/Engine/Source/Editor/Sequencer/Public/SequencerKeyCollection.h
Search forwards or backwards for the next key from the specified frame number
(Optional) Frame number of the key that's next or previous from that time
[TOptional](API\Runtime\Core\IO\TOptional)< [FFrameNumber](API\Runtime\Core\Misc\FFrameNumber) > GetNextKey ( [FFrameNumber](API\Runtime\Core\Misc\FFrameNumber) FrameNumber, EFindKeyDirection Direction ) const